Spring calculators:How can they be so vastly different?

It’s a great question. I’ve thought about it myself before and figured there are a variety of reasons.

Different companies have a different take on what good looks like. Mojo for example always liked to sway people towards a firmer ‘race’ set up (something about the bike skimming over the tops of bumps at speed rather than falling into them), whereas TF were of the view that few of their customers were actually riding at the sorts of speeds where that becomes relevant and so were more inclined to go with comfort than speed.

Different dampers have different ways of working internally; the Cane Creek has much more oil flow (apparently) and therefore more of the spring rate can be taken by the oil resulting in a lower coil rate being needed.

There will be differences in the assumptions made about the leverage ratios in bike design. For instance, TF only differentiates between single pivot and multi-link but not all multi link bikes have the same mechanical leverage curves.

Also assumptions about what type of riding the bike will be used for. Cane Creek for instance differentiate between trail/enduro and AM riding as well as DH and freeride, whereas TF only differentiate between trail, DH and freeride.

It does seem to be, basically, cobblers. I reckon there’s just more factors than the calculators can manage- like, all 4-bar bikes with a shock X length are not the same, pivot locations, lever lengths etc will all mess things up. Really I reckon it falls to manufacturers to know their bikes- I got perfect advice from Last, while Orange just said “use the TF calculator” which turned out to be hopeless.

TFtuned and Cane Creek give me a spring weight of 500, but jtech and mojo have me at 620, that is over two sizes different and would give a massively different shock feel. I’m swaying more towards tf and CC, but why such a discrepancy?